Environmental Engineering Reference
In-Depth Information
fore extrapolation of this data would be unwise. Understanding the size dependent
differences between bulk and nanoscale properties is important for shaping future
experiments in environmental nanoscience, as well as for the design of well-
informed nanotechnology legislation.
In this review, an attempt is made to link what is currently known about the size
dependent behaviour of inorganic nanoparticles and how this knowledge might
apply in environmental or natural systems. Size and shape effects upon redox/
catalysis chemistry, sorption processes and dissolution are reviewed, and sugges-
tions made on what sorts of future studies are necessary to answer the following
question: How will nanoparticles behave differently from their bulk counterparts,
and what might their environmental fate and impact be?
3.2
Inorganic Nanoparticle Anatomy
In environmental nanoscience, it is critical to understand that nanoparticles can
display an astoundingly broad range of physical and chemical properties. This
variety of properties generally results from differences in structure and composi-
tion between different nanoparticles. Therefore, to understand the behaviour of any
given type of nanoparticle, its structural and chemical characteristics must be
known.
While these characteristics are addressed in more detail in Chapter 2, they are
briefl y reviewed here for inorganic nanoparticles in terms of environmental behav-
iour (organic nanoparticles are covered in more detail in Chapter 4). Commercial
nanoparticles are composed of a core material and often a coating (although this
is optional), as shown in Figure 3.1. This core material can in theory be any solid
inorganic substance, although those most under development for applications (see
Chapters 1 and 2 for more information) include metals (gold, silver, palladium and
platinum) and semiconductors/insulators (metal sulfi des, selenides and oxides). The
core material can vary in both size and shape and confers many of the nanoparti-
Metals
oxides
sulfides
etc.
2. Size of
core
particle
1. Composition
of core particle
material
3. Core
particle
shape
5. Aggregation
4. Surface coating /
functionalization on
material
(nothing, molecules,
polymer…)
Aggregated
Dispersed?
Figure 3.1 Flow diagram displaying variables in the 'anatomy' of a colloidal inorganic
nanoparticle.
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